Use of wireless circuit-switched connections for transferring information requiring real-time operation of packet-switched multimedia services

ABSTRACT

A system includes a terminal, a wireless access network, a multimedia core network and a network device, which connects the wireless access network to the multimedia core network, expanded location updating to the registration procedure of the multimedia core network, and performs double registration of the user to the multimedia core network. The terminal performs expanded location updating relaying the registration point identity of the multimedia core network, the user&#39;s phone number and the private user identity to the network device in connection with normal location updating signaling. In the double registration performed by the network device, two addresses are registered for the user of the terminal, one of which is associated with the domain name of the terminal in question or a numeric IP address, and the other to a domain name of the network device or a numeric IP address.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/161,253, filed Oct. 8, 2010, now pending, which is a U.S. nationalstage application filed under 35 U.S.C. §371 of International PatentApplication PCT/FI2007/050026, accorded an international filing date ofJan. 18, 2007, both of which are incorporated herein by reference intheir entireties.

BACKGROUND

1. Technical Field

The disclosed embodiments disclose a system and a method for usingcircuit-switched bearer services of public mobile phone systems fortransferring information requiring real-time operation ofpacket-switched media services.

2. Description of the Related Art

As the wireless access network it is possible to use radio networks ofpublic mobile phone systems, such as, for example, GSM, IS-54, IS-95,CDMA-2000 and WCDMA radio networks, as well as radio networks usingunlicensed radio frequencies, such as, for example, a wireless localarea network in its different forms (for example different versions ofIEEE 802.11) and Bluetooth networks. The access networks can be used inboth a circuit-switched mode (radio networks of public mobile phonesystems) and a packet-switched mode (radio networks using unlicensedradio frequencies) for circuit-switched services (reference: UMA). UMA(Unlicensed Mobile Access) refers to a manner specified by the UMAconsortium for relaying the circuit-switched signaling protocols of apublic mobile phone system over a TCP/IP connection by utilizing, forexample, any unlicensed radio frequency. The packet-switched multimediaservice can be a generic IP telephone service according to IETF(Internet Engineering Task Force) specifications or a proprietary IPtelephone service, such as Skype. It can also be a multimedia service ofan IP Multimedia Subsystem (IMS) specified by 3GPP (the 3^(rd)Generation Partnership Project). The packet-switched multimedia serviceis based on combinations of audio, video, data and text, which arenormally used over a packet-switched transmission path and connectionalso for transferring information requiring real-time operation.

A central multimedia service is an IP telephone service, which willimplement, and possibly in the future also replace, conventionalcircuit-switched telephone services (i.e., teleservices) as well assupplementary services connected to them (i.e., call transfer, callholding/call pickup, etc.) in public mobile phone networks. However, inpublic mobile phone networks a General Packet Radio Service (GPRS) isnot necessarily the best possible or the most cost-effective way torelay information requiring real-time operation, such as audio andvideo, over a wireless access network. In a core network apacket-switched transfer method based on data network protocols of priorart is a useful and cost-effective way to relay information requiringreal-time operation, but for a wireless access network this is not thecase, not necessarily even in access networks using unlicensed radiofrequencies, when large numbers of users are involved. Thepacked-switched transfer method in wireless access networks of publicmobile phone systems is designed especially for transferring narrow-bandsound and images and it is the only way that is a verifiably functionaland cost effective way to transfer real-time audio and video in awireless manner when large numbers of users are involved. This issue isdiscussed in 3GPP as well, where specification work for joint use ofpacket-switched bearer services and IP multimedia subsystem session hasbeen started.

Publications US 2003/0027569 A1, US 2003/0027595 A1 and US 2003/0026245A1 disclose a system and a new entity (iMSC), by means of which thecircuit-switched services of a public mobile core network can beimplemented in the IP Multimedia Subsystem (IMS) specified by the 3GPP(3^(rd) Generation Partnership Project). The publications disclose a newentity called iMSC, which converts the circuit-switched locationupdating and the voice service and feature control into SIP operationsaccording to an IP multimedia subsystem. The publications do notdirectly describe how the conversion is performed, but they refer toknown operation modes of a public mobile phone network and to the knownoperations of the elements of a public mobile phone system.

For example, the publications disclose that the iMSC performsregistration of the user equipment (UE) in the IP multimedia subsystem,but they do not disclose which public user identity the iMSC registersin the IP multimedia subsystem for the user's terminal nor which addresssaid public user identity is connected to by means of the addressconnection being registered. In accordance with the recommendations ofthe IP multimedia subsystem of 3GPP—to which the publicationsrefer—there may be several registered public user identities and theymay be in the form of a SIP resource identifier (SIP URI, UniformResource Identifier) or a uniform resource locator meant for a telephonenumber.

The above-mentioned public user identities are stored in anIP-multimedia-subsystem-specific subscriber identity module (SIM) card.If no public user identities are specified, one public user identity isderived according to the 3GPP recommendations from the InternationalMobile Subscriber Identity (IMSI) of the user, which is then registeredin the IP multimedia subsystem. IMSI specifies the subscriber connectionunambiguously, but IMSI is not a telephone number with which or to whichit is possible to call from a conventional mobile phone or telephonenetwork, and not necessarily even within the IP multimedia subsystem. Ingeneric IP telephony networks the spectrum of public user identities iseven wider, when proprietary systems, such as Skype, are also taken intoaccount.

If now a mobile phone number is registered in the IP multimediasubsystem as the user's public address and the domain name of the iMSCas the address connection, as a person skilled in the art can assumefrom the operational descriptions of the publications in question and onthe basis of the recommendations of 3GPP and IETF—and which is anabsolute condition for the solution disclosed in the publications toeven function—it still remains unclear how the address connectionregistered for the user is provided to the ENUM/DNS service. It is notspecified in the recommendations of 3GPP or IETF either.

For the part of call control the operation of the conversion isdescribed in FIG. 3 of the publications, where the operation of iMSC isdescribed by two known elements ‘MSC Server’ and ‘P-CSCF’. A personskilled in the art can, on the basis of the publications, assume thatreference is made to elements specified in the 3GPP recommendations andtheir operation, in which case it remains unclear how the conversion ismade, because neither of the above-mentioned elements supports theconversion of call control signaling in any way as such, and in thepublications in question the way the conversion is made is not specifiedas a new operation for said elements. Elsewhere in the publications itis disclosed that the iMSC behaves like a combination of a SIP UserAgent, (SIP UA) and ‘P-CSCF’. Further, a person skilled in the art can,on the basis of the publications, assume that reference is made toelements specified in the 3GPP recommendations and their operation, inwhich case it remains unclear how, for example, the conversion of a callcontrol signaling is made, because neither of the above-mentionedelements supports the conversion of call control signaling in any way assuch according to the 3GPP recommendations, and in the publications inquestion the way the conversion is made is not specified as a newoperation for said elements.

For the part of call control signaling a more operative combinationwould be, according to the 3GPP recommendations and imitating thepublications in question, for example, a combination of‘MSCServer-T-SGW’-‘MGCF’-‘B-CSCF’or ‘MSC Server’-‘T-SGW’-‘MGCF’. Thesame applies for the conversion of circuit-switched supplementaryservices. For the part of SIP registration the above-mentionedcombination of the SIP user agent and ‘P-CSCF’ would be more operativefrom the point of view of the SIP connection procedure, if the interfacebetween iMSC and the ‘C-CSCF’ entity mentioned in the publicationswould, in accordance with the 3GPP recommendations, be Gm. The interfacebetween iMSC and the ‘C-CSCF’ entity is now specified by a new interface‘Mx’. In the publications the interface is specified as an interfaceusing the SIP connection procedure according to the procedures of the IPmultimedia subsystem, there are no other specifications for it and inthe 3GPP recommendations the interface in question does not exist. Inaddition, the SIP user agent and ‘P-CSCF’ do not as such support theconversion of the location updating signaling in any way according tothe 3GPP recommendations.

Further, in connection with the location updating of the mobile phonenetwork and registration to the IP multimedia subsystem, FIG. 4 of thepublications shows that the location updating to the mobile phonenetwork is performed first and then the registration to the IPmultimedia subsystem. This may lead to an unfortunate situation for theuser: if the location updating to the mobile phone network is nowsuccessful, but registration to the IP multimedia subsystem fails, theresult is a situation where no calls can be made with the terminal inquestion and no calls are received in it, because the user in questionhas not registered to a core network, i.e., the IP multimedia subsystem.The situation cannot be rectified until the terminal performs a periodiclocation updating or the user switches the terminal off and on again, inwhich case the registration to the IP multimedia subsystem is attemptedagain. In paragraph [0059] of the publication US 2003/0026245 A1, ismentioned the procedure ‘inter-iMSC Location Update’ of the 3GPPrecommendation TS 24.008, which, however, is not specified in therecommendation in question, nor is, for example, the ‘inter-MSC LocationUpdate’ procedure. The same procedure is mentioned in the otherabove-listed publications as well.

The publication mentions the iMSC entity performs the authentication ofthe user, for example, paragraphs [0057] and [0059] of US 2003/0026245A1, which on the basis of the description in the publication is anauthentication based specifically on the procedures of a conventionalmobile phone network, i.e., authentication performed by the visitorlocation register VLR on the basis of authentication parameters receivedfrom the home location register HLR over the MAP interface, and not anauthentication performed by an IP multimedia subsystem. This assumptionis also supported by the description of the operation in paragraph[0098] of US 200370026245 A1 (which description of operation can befound in the other publications as well): iMSC entity sends an SIPregistration request to the ‘CSCF’ (first to ‘I-CSCF’, which sends therequest further to ‘S-CSCF’), after which the ‘CSCF’s should performauthentication of the terminal through the iMSC entity by using the SIPauthentication procedure of the IP multimedia subsystem and only thenbring the SIP registration to a finish with ‘HSS’.

Publication US 2005/0083909 discloses a system, a device and a methodfor establishing a circuit-switched connection by using packet-switchedconnection establishing signaling. The discloses system includesterminals, a multimedia network, such as the IP multimedia subsystemspecified by 3GPP, and a conventional circuit-switched mobile phonenetwork, which is not described more in detail in the publication. Thepublication discloses new functions for the terminals, not for anynetwork elements.

BRIEF SUMMARY

Now the disclosed embodiments make it possible to combine twocost-effective ways that have been proven usable in practice forimplementing multimedia services in wireless access networks of publicmobile phone systems, i.e., a circuit-switched connection fortransferring information requiring real-time operation and apacket-switched connection for controlling multimedia services. Thedisclosed embodiments make it possible, for example, for mobile phoneservice providers to implement an IP multimedia subsystem and toimplement telephone services without having to invest in additionalcapacity of a wireless access network. In this case, the disclosedembodiments provide continuity in that it enables the joint use ofcircuit-switched bearer services and a session of the IP multimediasubsystem in accordance with the requirements specified by 3GPP as well.For the part of generic and proprietary IP telephone services, thedisclosed embodiments make it possible to combine a mobile phone numberto a generic or proprietary client of an IP telephone system, which islocated and used in a mobile phone. In other words, due to the disclosedembodiments, it is possible to call a client of a generic or proprietaryIP telephone system by using mobile phone numbers in the same way as inan IP multimedia subsystem.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a functional block chart of an overall system utilizing thedisclosed embodiments, when the IP telephone system is an IP multimediasubsystem according to 3GPP specifications.

DETAILED DESCRIPTION

The more specific structure and operation of the overall system of FIG.1 utilizing the invention is described with terms, interfaces andprotocols known from GSM and UMTS.

In the overall system according to FIG. 1 a circuit-switched wirelessaccess network (104) of a public mobile phone system is connected to anIP multimedia subsystem (101) via a multi bearer service gateway (MBSGW)(4). The circuit-switched wireless access network is formed by a basestation (1) as well as a base station/radio network controller (2),which is called a Base Station Subsystem (BSS) in the GSM system and aRadio Network System (RNS) in the third generation UMTS system. Thewireless access network (104) can also be formed by, for example, a UMAnetwork utilizing unlicensed frequencies, which network containswireless radio access points (AP) (30) as well as a UMA networkcontroller (31), or it can be formed of a generic access networkutilizing unlicensed frequencies, which is composed of wireless accesspoints (30). A mobile services switching center/visitor locationregister server (MSC Server) (5), a home location register (HLR) (7), anequipment identity register (EIR) (8), service and gateway nodes (SGSNand GGSN) (3) and (10) of a packet radio network, as well as an IPmultimedia subsystem (101), in turn, form the mobile core network. Themobile core network is divided into a circuit-switched part, whichcomprises the MSC Server (5) (this may naturally also be a conventionalcombination of a mobile services switching center and a visitor locationregister), a packet-switched part, which comprises service and gatewaynodes (3) and (10) of a packet radio network, a location register part,which comprises the home location register (7), the visitor locationregister (not shown separately in FIG. 1) and the packet radio networkservice and gateway nodes (3) and (10), as well as an IP multimediasubsystem (101), which includes a Home Subscriber Server (HSS) (11), aCall Session Control Function (CSCF) (9) in its different functionalforms (i.e., I-CSCF, P-CSCF, S-CSCF and B-CSCF), a Media Gateway ControlFunction (MGCF) (14), a Media Gateway (MGW) (15), as well as aMultimedia Resource Function (MRF) (16).

In the following the interfaces of the multi bearer service gatewayaccording to the disclosed embodiments of FIG. 1 will be described morein detail.

When the wireless access network (104) of the public mobile phone systemof FIG. 1 is connected via an interface A (50) or luCS (71) to a multibearer service gateway (4), the wireless access network (104) sees themulti bearer service gateway (4) and the IP multimedia subsystem (101)behind it as an MSC Server (5) of the public mobile phone system, i.e.,as a circuit-switched part of the public mobile core network. It shouldbe noted that, for example, the interface (50) can be either a real GSMA interface, or it can be a distributed A interface in such a mannerthat the lower protocols of the A interface (for example, MTP and SCCPprotocols) are implemented with an SS7oIP gateway utilizing the known‘SS7 over IP’ gateway technique (not shown in FIG. 1) and the upperprotocols of the A interface (for example BSS-MAP and DTAP protocols) inthe multi bearer service gateway (4), which also supports theabove-mentioned ‘SS7 over IP’ gateway technique. If the basestation/radio network controller (2) of the wireless access network(104) also supports the above-mentioned ‘SS7 over IP’ gateway technique,said SS7oIP gateway is not needed in the interfaces A (50) and IuCS(71). Said ‘SS7 over IP’ gateway technique is a method specified byIETF, including protocols (i.e., Sigtran protocols), for transferringSS7 signaling by utilizing the IP connection protocol. Via the interfaceUp (52) the terminal (6) sees the multi bearer service gateway (4) andthe IP multimedia subsystem (101) behind it as a UMA network controllerand as an MSC Server (5) of a public mobile phone system, i.e., as acircuit-switched part of the public mobile core network. Via theinterface U (70) the terminal (6) sees the multi bearer service gateway(4) and the IP multimedia subsystem (101) behind it as an MSC Server (5)of a public mobile phone system over a TCP/IP (or the like) connectionwhen the terminal (6) performs location updating to a public mobilephone system. It is to be noted that in this case the terminal (6) musthave adequate properties to activate and perform the location updatingprocedure to the mobile phone system over, for example, theabove-mentioned TCP/IP (or the like) connection.

Via the interface Gm (61) of FIG. 1 the session control function (9) ofthe IP multimedia subsystem (101) sees the multi bearer service gateway(4) as User Equipment (UE) of the IP multimedia subsystem (101), i.e.,as a terminal (6) that is compatible with the IP multimedia subsystem(101), which normally communicates with the session control function (9)of the IP multimedia subsystem via the packed radio network gateway node(10). Via the interface Mn (62) the media gateway (15) sees the multibearer service gateway (4) as a media gateway control function (14).

The multi bearer service gateway (4) according to the disclosedembodiments comprise the following functions. A UNC GW function (18)comprises a UMA radio resource protocol gateway, via which the terminal(6) equipped with UMA properties registers and communicates with themulti bearer service gateway (4) and through that with the IP multimediasubsystem (101). The multi bearer service gateway (4) does not implementthe actual UMA network controller, but therefore only the UMA radioresource protocol gateway. A SIP GW function (20) comprises a SIPgateway, which implements the functions of the user equipment accordingto SIP specifications of 3GPP, as well the control of useridentification data and the addresses-of-record of the IP multimediasubsystem (101) and the address bindings connected to sessions. A SGWfunction (22) is the core of the protocol routing function of the multibearer service gateway (4). The SGW function (22) receives and relaysfurther the location updating, registering, identification, connection,disconnection requests and responses coming from and going to differentinterfaces.

FIG. 1 shows the terminal (6) control protocols substantial from thepoint of view of the disclosed embodiments. These include GPRS protocols(30), SIP/SDP protocols (+TCP/UDP/IP) (31), as well as protocols (32) ofthe circuit-switched part of the core network.

In the following the interfaces of the terminal according to thedisclosed embodiments of FIG. 1 will be described more in detail.

Via the interface Um (63) of FIG. 1 the base station subsystem of theGSM system sees the terminal (6) as a wireless GSM terminal, the servicenode (3) of the packet radio network sees the terminal (6) as a normalterminal of the packet radio network, the MSC Server (5) sees theterminal (6) as a terminal of the circuit-switched part of the corenetwork, and the session control function (9) of the IP multimediasubsystem (101) sees the terminal (6) as user equipment of the IPmultimedia subsystem (101). Via the interface Uu (64) the radio networksystem of the UMTS system sees the terminal (6) as a wireless UMTSterminal, the service node (3) of the packet radio network sees theterminal (6) as a normal terminal of the packet radio network, the MSCServer (5) sees the terminal (6) as a terminal of the circuit-switchedpart of the core network, and the session control function (9) of the IPmultimedia subsystem (101) sees the terminal (6) as user equipment ofthe IP multimedia subsystem (101). Via the interface Up (52) the servicenode (3) of the packet radio network sees the terminal (6) as a normalterminal of the packet radio network, the MSC Server (5) sees theterminal (6) as a terminal of the circuit-switched part of the corenetwork, and the session control function (9) of the IP multimediasubsystem (101) sees the terminal (6) as user equipment of the IPmultimedia subsystem (101). Via the interface U (70) the multi bearerservice gateway (4) sees the terminal as a terminal implemented over aTCP/IP (or the like) connection of location updating of thecircuit-switched part of the service network of the mobile phone system.

In the following, the function of the system according to the disclosedembodiments in connection with registering to the multimedia corenetwork is described more in detail. Description of the function isbased on functions according to 3GPP specifications, functions differingfrom standard functions are mentioned separately. As the multimedia corenetwork is disclosed a network according to the IP multimedia subsystem(101), but it can also be a generic IP voice and communication networkaccording to IETF (Internet Engineering Task Force) specifications or aproprietary network, such as Skype.

When the terminal (6) shown in FIG. 1 sends a location updating requestof the circuit-switched part of the mobile core network over theinterface Um (63), Uu (64), Up (50) or U (70) to the multi bearerservice gateway (4), the multi bearer service gateway (4) activates theregistration according to the SIP session procedure of 3GPP to the IPmultimedia subsystem (101) via the interface Gm (61). The multi bearerservice gateway (4) sets the home network registrar's domain name to theRequest URI (Uniform Resource Identifier) of the SIP registrationrequest, which domain name the multi bearer service gateway (4) derivesfrom the user's International Mobile Subscriber Identity (IMSI) from itscountry and network codes according to the 3GPP specifications. Themulti bearer service gateway (4) receives the user's internationalsubscriber identity from the terminal (6) in the location updatingrequest or the multi bearer service gateway (4) requests the terminal(6) to send it in an identity response, if the user's internationalsubscriber identity does not come with the location updating request.The multi bearer service gateway (4) can also request the home networkregistrar's domain name from the terminal (6) with an identity requestor the terminal (6) can send it in a location updating request. This,however, requires a change in the terminals (6) functioning according tostandard or a change in the standard itself, for example, in such amanner that a new, private information element for the home networkregistrar's domain name is specified for the location updating request,the identity request and the identity response. In the To header fieldof the SIP registration request the multi bearer service gateway (4)sets the registration address, which is the public user identity of theregistering user presented in the form of a uniform resource locator(URL) meant for a phone number, which in this case is the internationalmobile phone number (mobile station ISDN, MSISDN) of the above-mentionedregistering user. If the multi bearer service gateway (4) does not knowthe international mobile phone number of the user in question, the multibearer service gateway (4) can request it from the terminal (6) with anidentity request or the terminal (6) can send it in a location updatingrequest. This, however, requires a change in the terminals (6)functioning according to a standard or a change in the standard itself,for example, in such a manner that a new, private mobile identity valueand a new, private data structure is specified for the user'sinternational mobile phone number in the mobile identity field of thelocation updating request, the identity request and the identityresponse. In the From header field of the SIP registration request themulti bearer service gateway (4) sets the address connection connectedto the SIP session services of the user's SIP end point, which addressconnection follows the resource identifier structure according to theSIP session procedure, including the user's international mobile phonenumber as a character string+‘@’ character+domain name of the multibearer service gateway (4) or its numeric IP address. In the Contactheader field of the SIP registration request the multi bearer servicegateway (4) relays to the IP multimedia subsystem (101) the addressconnection connected to the SIP session services of the user's SIP endpoint, which address connection the multi bearer service gateway (4)also stores in its database (or a corresponding memory). Theabove-mentioned address connection of the session services of the SIPend point is the same as the address connection relayed in the Fromheader field, i.e., the user's international mobile phone number as acharacter string+‘@’ character+domain name of the multi bearer servicegateway (4) or its numeric IP address. In the Username field of theAuthorization header field the multi bearer service gateway (4) sets theprivate user identity of the user, which the multi bearer servicegateway (4) derives from the user's international subscriber identityfrom its country and network codes according to the 3GPP specifications.The multi bearer service gateway (4) can also request the private useridentity from the terminal (6) with an identity request or the terminal(6) can send it in a location updating request. This, however, requiresa change in the terminals (6) functioning according to a standard or achange in the standard itself, for example, in such a manner that a new,private mobile identity value and a new, private data structure isspecified for the private user identity in the mobile identity field ofthe location updating request, the identity request and the identityresponse. In the Realm field of the Authorization header field the multibearer service gateway (4) sets an identifier of that network where theuser authentication is performed. The network identifier in question isthe home network registrar's domain name, which the multi bearer servicegateway (4) can thus request from the terminal (6) as well with anidentity request or the terminal (6) can send it in a location updatingrequest. As already mentioned, this requires a change in the terminalsfunctioning according to a standard or a change in the standard itself.In the Request URI field of the Authorization header field the multibearer service gateway (4) sets the request URI of the SIP registrationrequest. In the Security-Client header field the multi bearer servicegateway (4) relays to the session control function (9) of the IPmultimedia subsystem (101) those data security mechanisms, which theterminal (6) supports and which are used between the terminal (6) andthe session control function (9). In this case the function differs fromthe mechanisms specified by 3GPP in that the data security mechanisms inquestion are used between the multi bearer service gateway (4) and thesession control function (9) of the IP multimedia subsystem (101), andbetween the terminal (6) and the multi bearer service gateway (4) areused the data security mechanisms of a circuit-switched wireless accessnetwork of a public mobile phone system. The ciphering procedure usedbetween the multi bearer service gateway (4) and the session controlfunction (9) is IPsec-3GPP and the integrity algorithm being used iseither HMAC-MD5-96 or HMAC-SHA-1-96 according to 3GPP specifications. Inaddition to these the multi bearer service gateway (4) relays in theother fields of the Security-Client header field the necessaryparameters for creating a secure and encrypted security associationbetween the multi bearer service gateway (4) and the IP multimediasubsystem (101), i.e., the Security Parameter Index (SPI) and thecommunication port numbers being used. After receiving the registrationrequest the session control function (9) of the IP multimedia subsystem(101) starts the authentication of the user of the terminal (6) (i.e.,the subscriber connection) by sending an unauthorized response to themulti bearer service gateway (4). In the WWW-Authenticate header fieldof the unauthorized response the session control function (9) relays arandom number (RAND), an authentication token (AUTN) and theauthentication algorithm to be used. In the Security-Server header fieldof the unauthorized response the session control function (9) relays theparameters of the ciphering procedure used between the multi bearerservice gateway (4) and the session control function (9), such as theciphering algorithm being used, the security parameter index and thecommunication port numbers being used. After receiving the unauthorizedresponse the multi bearer service gateway (4) sends a correspondingauthentication request to the terminal (6). In the authenticationrequest the multi bearer service gateway (4) relays a random number andan authentication token to the terminal (6) as well as identifies theauthentication algorithm to be used. After receiving the authenticationrequest the terminal (6) picks the Message Authentication Code (MAC) andthe Sequence Number (SQN) from the authentication token, calculates theExpected MAC, compares it to the authentication code of the receivedmessage and checks that the sequence number is within allowed limits. Ifthe results are positive, the terminal (6) calculates the authenticationchallenge response (RES) and sends the authentication challenge responseto the multi bearer service gateway (4) in its authentication requestresponse. After receiving the authentication request response the multibearer service gateway (4) stores the user authentication etc. data in adatabase (or a corresponding memory), creates an Integrity Key (IK) andsecurity parameter index, as well as a secure and encrypted networkconnection and sends a new SIP registration request to the sessioncontrol function (9) of the IP multimedia subsystem (101) over thesecure and encrypted network connection, which is established betweenthe multi bearer service gateway (4) and the session control function(9). The multi bearer service gateway (4) adds the private user identityand authentication challenge response to the Authorization header field.The content of the Security-Client header field is the same as in thefirst SIP registration request. The multi bearer service gateway (4)also adds the Security-Verify header field to the new SIP registrationrequest in question, which contains the contents of the Security-Serverheader field received in the unauthorized response in an unchanged form.When the multi bearer service gateway (4) receives the OK response fromthe session control function (9), the registration to the IP multimediasubsystem (101) has succeeded. If the Contact header field of thereceived OK response now also has some other address connection than theabove-mentioned registered address connection addressing the multibearer service gateway (4) in question, which connection follows theresource identity structure according to the SIP session procedureincluding the user's international mobile phone number as a characterstring+‘@’ character+some domain name or a numeric IP address, i.e., theprevious registration to the IP multimedia subsystem (101) via someother multi bearer service gateway, that other address connection isremoved by sending a registration request to the IP multimedia subsystem(101), the expiration time of which request is 0 seconds and the Contactheader field now has that other address connection. The multi bearerservice gateway (4) further registers another public used identity forthe same user, which is now in the form of a Uniform Resource Identifieraccording to SIP session procedure including the resource identifier ofthe international mobile phone number of the user in question in theUserinfo field and the domain name of the multi bearer service gateway(4) or its numeric IP address in the Resource Identifier Host field. Theresource identifier is shown in the form ‘userinfo@host’, in practicethe resource identifier is therefore the same as the address connectionof the previous registration. The public user identity in question isset in the To header field of the new SIP registration request.Otherwise the SIP registration request is formed in the same way asabove. With these two different registrations, a readiness for the jointuse of circuit-switched bearer services and SIP session is created. Whenthe multi bearer service gateway (4) receives the OK response from thesession control function (9), the registration of the second public useridentity to the IP multimedia subsystem (101) has succeeded, after whichthe multi bearer service gateway (4) sends a location updating responseindicating acceptance to the terminal (6). If the Contact header fieldof the received new OK response now also has some other addressconnection than the above-mentioned registered address connectionaddressing the multi bearer service gateway (4) in question, whichconnection follows the resource identity structure according to the SIPsession procedure including the user's international mobile phone numberas a character string+‘@’ character+some domain name or a numeric IPaddress, that other address connection is removed by sending aregistration request to the IP multimedia subsystem (101), theexpiration time of which request is 0 seconds and the Contact headerfield now has that other address connection. If the SIP registrationfails for some reason, the multi bearer service gateway (4) rejects thelocation updating and signals the rejection to the terminal (6). Whenthe registration to the IP multimedia subsystem (101) has been performedvia the multi bearer service gateway (4), the terminal (6) registers tothe IP multimedia subsystem (101) in the normal manner specified by 3GPPover the packet radio network with one or more registration addresses,one of which is the public user identity of the registering user shownin the form of a resource locator meant for a phone number. In this casethe public user identity in question is the same as the public useridentity used in the first registration taking place via the multibearer service gateway (4). The registration address is set in the Toand From header fields of the registration request. In the Contactheader field of the registration request the terminal (6) relays to theIP multimedia subsystem (101) its own address connection connected toSIP session services, which connection is a domain name of the terminal(6) in the form of a resource identifier or a numeric IP address, andwhich connection is now set as the more privileged address connectionfor the public user identity in question. The IP multimedia subsystem(101) authenticates the user, switches the data security mechanisms on,and accepts the registration by sending an OK response to the terminal(6). The Contact header field of the OK response now has at least twoaddress connections for the public used identity in question, one ofwhich is the above-mentioned terminal's (6) own address connectionconnected to SIP session services and one an address connectionaddressing the multi bearer service gateway (4).

In the following, the functions connected to phone callestablishing/cancellation are described more in detail.

When the user of the terminal (6) of FIG. 1 starts an IMS call, theterminal (6) sends an SIP session request in a normal manner accordingto 3GPP specifications over the packet radio network to the sessioncontrol function (9) of the IP multimedia subsystem (101). The SIPsession request is formed in a normal manner including the message bodyfor session media description. The session control function (9) of theIP multimedia subsystem (101) responds to the session request first witha temporary response, then with a propagation response after receivingthe propagation response in question from the user equipment to bereached or from another session control function (not shown in FIG. 1).The propagation response includes the message body for media descriptionprovided by the user equipment to be reached. After this the terminal(6) starts a normal circuit-switched phone call setup, where theinternational mobile phone number of the user of the terminal (6) inquestion is set as the phone number of the user to be reached. Afterreceiving the phone call setup request via the interface A (50), luCS(71) or Up (52), the multi bearer service gateway (4) forms a SIPsession request to be sent to the session control function (9) of the IPmultimedia subsystem (101). To the request URI of the session requestthe multi bearer service gateway (4) sets the phone number of the userto be reached in the form of a resource locator meant for telephonenumbers. The phone number of the user to be reached is received from thephone call setup request received from the terminal (6). In the Toheader field the multi bearer service gateway (4) sets the public useridentity of the user to be reached, i.e., the registration address,which is in the form of a resource locator meant for telephone numbersand includes the phone number of the user to be reached received in thephone call setup request. In the From header field the multi bearerservice gateway (4) sets the caller's phone number in the form of aresource locator meant for phone numbers, which now is the terminal (6)user's own international mobile phone number and which the multi bearerservice gateway (4) receives from the phone call setup request from theterminal (6). In the Contact header field the multi bearer servicegateway (4) sets the address connection connected to the sessionservices of the caller's SIP end point, which connection it stored inconnection with registration (i.e., the same as the registration addressof the caller in the From header field). The session request alsoincludes the message body for session media description. The media isdescribed with a set of parameters, which specify, inter alia, thenetwork type, the domain name of the caller's SIP end point, the domainname of the used media gateway, the media type, the media relayprotocol, and the media coding method. The domain name of the caller'sSIP end point is the domain name of the multi bearer service gateway (4)in question. The domain name of the media gateway (15) being used isreceived from the system configuration data. The media coding method isreceived from the phone call setup request received from the terminal(6). The multi bearer service gateway (4) sends a session request to thesession control function (9) of the IP multimedia subsystem (101) viathe interface Gm (61). After receiving the SIP session request thesession control function (9) first sends a temporary response to themulti bearer service gateway (4) after which it sends the SIP sessionrequest to the terminal (6) in a normal manner over the packet radionetwork, because the address connection registered by the terminal (6)for the public user identity of the caller in the To header field is aprivileged address connection. After receiving the SIP session requestthe terminal (6) responds with an OK response, which includes theselected message body for media description, which in turn includes thedomain name of the SIP end point of the user to be reached with theoriginal IMS call initiated by the terminal (6), the media relayprotocol being used, the coding method, the network type, as well as thedomain name of the media gateway being used in connection with theabove-mentioned user to be reached. The session control function (9)relays the OK response to the multi bearer service gateway (4), fromwhere the multi bearer service gateway (4) picks and stores the data ofthe message body for media description connected to the SIP end point ofthe user to be reached with the original IMS phone call initiated by theterminal (6) and creates a voice connection between the media gatewaynotified by the user to be reached in question and the media gateway(15) allocated by the multi bearer service gateway itself, after whichit creates a Connect response of the circuit-switched phone call andsends it to the terminal (6). After receiving the phone call connectresponse from the multi radio protocol gateway (4) the terminal (6)sends an IMS phone call propagation acknowledgement (PRACK) to thesession control function of the IP multimedia subsystem (101), in themessage body for media description of which the terminal (6) now relaysthe domain name of the multi bearer service gateway (4), the relayprotocol of the media being used, the coding method, the network type,and the domain name of the media gateway (15) being used. In theoriginal IMS phone call initiated by the terminal (6) the SIP end pointof the user being reached can now open a voice connection to the mediagateway (15) notified by the multi bearer service gateway (4). When theSIP end point of the user to be reached with the IMS phone call sendsthe final OK response, the SIP session has been established between theterminal (6) and the SIP end point of the user to be reached in such amanner that voice (and image) travels between the media gateway (15)allocated by the multi bearer service gateway (4) and the media gatewayallocated by the user to be reached. Between the terminal (6) and themedia gateway (15) allocated by the multi bearer service gateway (4) theaudio (and the video) travels in a wireless manner over the accessnetwork by using the circuit-switched bearer service specified by theSIP session. Cancellation of the connection takes place in acorresponding manner by signaling it between the IP multimedia subsystem(101) and the terminal (6) in such a manner that both the SIP sessionand the circuit-switched bearer service connection are cancellednormally separately. It is to be noted that the establishing of acircuit-switched bearer service, i.e., a normal circuit-switched phonecall, can be made after any response according to the SIP sessionprocedure, which response includes the data of the message body formedia description connected to the SIP end point of the user to bereached with the original IMS phone call initiated by the terminal (6).In addition, the circuit-switched connection can be established so thatafter receiving the propagation response to the IMS phone call from thesession control function (9) of the IP multimedia subsystem (101) theterminal (16) sends a SIP session request normally according to 3GPPspecifications over the packet radio network to the session controlfunction (9) of the IP multimedia subsystem (101), the To header fieldof which SIP session request now includes the public user identity ofthe terminal (6) in question, which in turn is the address connectionaddressing the multi bearer service gateway (4), which the terminal (6)received in connection with registration, and the From header fieldincludes the terminal (6) user's own international mobile phone number,i.e., the registered public user identity, in the form of a resourcelocator meant for phone numbers. After receiving the SIP session requestthe session control function (9) of the IP multimedia subsystem (101)first sends a temporary response to the terminal (6), after which itsends a SIP session request to the multi bearer service gateway (5) viathe interface Gm (61). In the SIP session request the terminal (6)relays to the multi bearer service gateway (4) the data of the messagebody for media description connected to the SIP end point of the user tobe reached with the original IMS phone call initiated by the terminal(6), which data the multi bearer service gateway (4) uses for creatingan audio (and video) connection to the media gateway allocated by theSIP end point in question. After receiving the SIP session request themulti bearer service gateway (4) first performs a paging procedure viathe interface A (59), luCS (71) or Up (52), with which the terminal (6)is made to receive a circuit-switched phone call setup request, if theconnection between the terminal (6) and the multi bearer service gateway(4) is not already active. When the terminal (6) has answered the page,the multi bearer service gate (4) relays the circuit-switched phone callsetup request to the terminal (6), after which the phone callestablishing is signaled between the terminal (6) and the IP multimediasubsystem (101) via the multi bearer service gateway (4). In the firstSIP session request response, where the message body for mediadescription is allowed, the multi bearer service gateway (4) relays tothe terminal (6) the data of the message body for media descriptionbeing used in connection with the multi bearer service gateway (4),which data the terminal (6) relays further to the SIP end point of theuser to be reached with the original IMS phone call initiated by theterminal (6). This latter manner for establishing a circuit-switchedconnection over the wireless access network (104) is inferior in that ituses more of the resources of the wireless access network (104). Theterminal (6) knows how to connect the circuit-switched connectionestablishing to the SIP session establishing, because thecircuit-switched connection establishing is made with it to the publicuser identity that has (at least) two address connections, one of whichis the address connection connected to the SIP session services andregistered to it by the terminal (6) itself and one is the addressconnection addressing the multi bearer service gateway (4) in questionand registered to it by the multi bearer service gateway (4). It is tobe noted that both the wireless access network (104) and the terminal(6) must have the ability for the simultaneous use of circuit- andpacket-switched bearer services. It is also to be noted that the sessioncontrol function (9) of the IP multimedia subsystem (101) does notnecessarily have to have any special knowledge or properties for thejoint use of the circuit-switched bearer services and the SIP session,because in this case the session control function (9) sees the joint useas two separate SIP sessions.

The phone call can also be established from the IP multimedia subsystem(101) to the terminal (6).

When the terminal (6) of FIG. 1 receives the SIP session request fromthe session control function (9) of the IP multimedia subsystem (101),the terminal (6) sends a temporary response to the session controlfunction (9). After this the terminal (6) starts a normalcircuit-switched phone call setup, where the international mobile phonenumber of the user of the terminal (6) in question is set as the phonenumber of the user to be reached. The circuit-switched connection isestablished as described above in connection with the function connectedto phone call establishing. When the circuit-switched connection hasbeen established, the terminal (6) sends a propagation response to thesession control function (9) of the IP multimedia subsystem (101), whichpropagation response includes a message body for media description,where the terminal (6) now relays to the SIP end point of the callinguser the domain name of the multi bearer service gateway (4), the relayprotocol of the media being used, the coding method, the network type,and the domain name of the media gateway (15) being used. The SIP endpoint of the calling user responds with a propagation acknowledgement,after which it can send an updating request (UPDATE), where it can, forexample, specify the parameters of the media being used. The terminal(6) forms and sends a corresponding updating request to the multi bearerservice gateway (4) which detects the new media parameters and respondswith an OK response to the terminal (6), which in turn responds with anOK response to the SIP end point of the user calling via the connectioncontrol function (9) to the updating request sent by it (if such camefrom the SIP end point of the calling user, that is). When the user ofthe terminal (6) responds to the IMS phone call, the terminal (6) sendsthe final OK response to the session control function (9) and further tothe SIP end point of the calling user, which responds by sending anacknowledgement response to the terminal (6). When the terminal (6) hasreceived an acknowledgement response to the final OK response it hassent, the SIP session has been established between the SIP end point ofthe calling user and the terminal (6) and the circuit-switchedconnection with the terminal (6) and the multi bearer service gateway(4) (and the media gateway (15)).

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A method of operation in a mobile radio terminal to providecommunications between the mobile radio terminal and a multimedia corenetwork via a wireless access network and a multi bearer service gatewaynetwork device, which multi bearer service gateway network deviceperforms a double registration of the mobile radio terminal, the methodcomprising: wirelessly transmitting a registration request to the multibearer service gateway network device by the mobile radio terminal viathe wireless access network; generating by the mobile radio terminal atleast one of a location updating request, an identity request, or anidentity response to an identity request which includes a privateinformation element specified for a domain name of a home registrar of auser account; and wirelessly transmitting by the mobile radio terminalvia the wireless access network the at least one of the locationupdating request, the identity request, or the identity response whichincludes the specified private information element to the multi bearerservice gateway network device.
 2. The method of operation of claim 1wherein wirelessly transmitting the at least one of the locationupdating request, the identity request, or the identity responseincludes wirelessly transmitting the location updating request whichincludes the specified private information element via a circuitswitched wireless access network.
 3. The method of operation of claim 1,further comprising: receiving a request by the mobile radio terminal,the request initiated by the multi bear service gateway; and wherein thegenerating and wirelessly transmitting the at least one of the locationupdating request, the identity request, or the identity response whichincludes the private information element to the multi bearer servicegateway network device is responsive to the received request.
 4. Themethod of operation of claim 1 wherein wirelessly transmitting the atleast one of the location updating request, the identity request, or theidentity response includes wirelessly transmitting the location updatingrequest which further includes a private mobile identity value and aprivate data structure specified for an international mobile phonenumber associated with the user account.
 5. The method of operation ofclaim 4 wherein wirelessly transmitting the location updating requestwhich further includes a private mobile identity value and a privatedata structure specified for an international mobile phone numberassociated with the user account includes transmitting the locationupdating request which includes a mobile subscriber integrated servicesdigital network number (MSISDN) associated with the user account.
 6. Themethod of operation of claim 1, further comprising: receiving a requestby the mobile radio terminal, the request initiated by the multi bearservice gateway; generating by the mobile radio terminal at least one ofan identity request or an identity response to an identity request whichincludes a private mobile identity value and a private data structurespecified for an international mobile phone numbers associated with theuser account; and wirelessly transmitting by the mobile radio terminalvia the wireless access network the at least one of the identity requestor the identity response which includes the private mobile identityvalue and a private data structure specified for an international mobilephone numbers associated with the user account to the multi bearerservice gateway network device.
 7. The method of operation of claim 6wherein generating at least one of an identity request or an identityresponse to an identity request which includes a private mobile identityvalue and a private data structure specified for an international mobilephone numbers associated with the user account includes generating theat least one of the identity request or the identity response to theidentity request which includes the private mobile identity value andthe private data structure specified for a mobile subscriber integratedservices digital network number (MSISDN) associated with the useraccount.
 8. The method of operation of claim 1 wherein wirelesslytransmitting the at least one of the location updating request, theidentity request, or the identity response includes wirelesslytransmitting the location updating request which further includes aprivate mobile identity value and a private data structure specified fora private user identity associated with the user account.
 9. The methodof operation of claim 8 wherein wirelessly transmitting the locationupdating request which further includes a private mobile identity valueand a private data structure specified for a private user identityassociated with the user account includes transmitting the locationupdating request with the private mobile identity value and the privatedata structure specified for an international mobile subscriber identity(IMSI) number associated with the user account.
 10. The method ofoperation of claim 1, further comprising: receiving a request by themobile radio terminal, the request initiated by the multi bear servicegateway; generating by the mobile radio terminal at least one of anidentity request or an identity response to an identity request whichincludes a private mobile identity value and a private data structurespecified for a private user identity associated with the user account;and wirelessly transmitting by the mobile radio terminal via thewireless access network the at least one of the identity request or theidentity response which includes the private mobile identity value andthe private data structure specified for the private user identityassociated with the user account to the multi bearer service gatewaynetwork device.
 11. The method of operation of claim 10 whereinwirelessly transmitting the at least one of the identity request or theidentity response which includes the private mobile identity value andthe private data structure specified for the private user identityassociated with the user account includes wirelessly transmitting the atleast one of the identity request or the identity response whichincludes the private mobile identity value and the private datastructure specified for an international mobile subscriber identity(IMSI) number associated with the user account.
 12. The method ofoperation of claim 1, further comprising: receiving multimedia by themobile radio terminal from a packet switched multimedia domain via acircuit switched wireless access domain.
 13. A mobile radio terminal toprovide communications between the mobile radio terminal and amultimedia core network via a wireless access network and a multi bearerservice gateway network device, which multi bearer service gatewaynetwork device performs a double registration of the mobile radioterminal, the mobile radio terminal comprising: a radio; and acontroller communicatively coupled to the radio and configured to: causethe radio to wirelessly to transmit a registration request to the multibearer service gateway network device via the wireless access network;generate at least one of a location updating request, an identityrequest, or an identity response to an identity request which includes aprivate information element specified for a domain name of a homeregistrar of a user account; and cause the radio to wirelessly transmitvia the wireless access network the at least one of the locationupdating request, the identity request, or the identity response whichincludes the specified private information element to the multi bearerservice gateway network device.
 14. The mobile radio terminal of claim13 wherein the controller causes the radio to wirelessly transmit the atleast one of the location updating request, the identity request, or theidentity which includes the specified private information element via acircuit switched wireless access network.
 15. The mobile radio terminalof claim 13 wherein the controller generates the at least one of thelocation updating request, the identity request, or the identityresponse which includes a private mobile identity value and a privatedata structure specified for an international mobile phone numberassociated with the user account.
 16. The mobile radio terminal ofoperation of claim 15 the international mobile phone number associatedwith the user account includes a mobile subscriber integrated servicesdigital network number (MSISDN) associated with the user account. 17.The mobile radio terminal of claim 13, wherein in response to a receivedrequest initiated by the multi bear service gateway, the controller:generates at least one of an identity request or an identity response toan identity request which includes a private mobile identity value and aprivate data structure specified for an international mobile phonenumbers associated with the user account; and causes the radio towirelessly transmit via the wireless access network the at least one ofthe identity request or the identity response which includes the privatemobile identity value and a private data structure specified for aninternational mobile phone numbers associated with the user account tothe multi bearer service gateway network device.
 18. The mobile radioterminal of claim 17 wherein the controller generates the at least oneof the identity request or the identity response to the identity requestto include the private mobile identity value and the private datastructure specified for a mobile subscriber integrated services digitalnetwork number (MSISDN) associated with the user account.
 19. The mobileradio terminal of claim 13 wherein the controller causes the radio towirelessly transmit the at least one of the location updating request,the identity request, or the identity response which further includes aprivate mobile identity value and a private data structure specified fora private user identity associated with the user account.
 20. The mobileradio terminal of claim 19 wherein the controller causes the radio towirelessly transmit the location updating request which further includesa private mobile identity value and a private data structure specifiedfor an international mobile subscriber identity (IMSI) number associatedwith the user account.
 21. The mobile radio terminal of claim 13 whereinin response to a received request initiated by the multi bear servicegateway, the controller generates at least one of an identity request oran identity response to an identity request which includes a privatemobile identity value and a private data structure specified for aprivate user identity associated with the user account; and causes theradio to wirelessly transmit via the wireless access network the atleast one of the identity request or the identity response whichincludes the private mobile identity value and the private datastructure specified for the private user identity associated with theuser account to the multi bearer service gateway network device.
 22. Themobile radio terminal of claim 21 wherein the controller causes theradio to wirelessly transmit the at least one of the identity request orthe identity response which includes the private mobile identity valueand the private data structure specified for an international mobilesubscriber identity (IMSI) number associated with the user account. 23.The mobile radio terminal of claim 13 wherein the radio receivesmultimedia by the mobile radio terminal from a packet switchedmultimedia domain via a circuit switched wireless access domain.